1. Field of the Invention
The present invention generally relates to a multi-program execution controlling apparatus and method, and more particularly to a multi-program execution controlling apparatus and method which inhibit a program currently being executed from unnecessarily accessing another program in a one-chip microcomputer having a plurality of programs.
2. Description of the Related Art
For portable data carriers, such as IC cards or wireless cards, the security of their programs and data has been considered important.
In one-chip microcomputers used for such portable data carriers, a single main program is allocated to a single semiconductor chip. Even when it has a plurality of programs, these programs are used to act as extension of the main program or part of the main program's function in the form of subroutines.
With program execution controlling techniques for such one-chip microcomputers, the identification (ID) information on the running ones of the plurality of programs are sent to the central processing unit (CPU) in the one-chip microcomputer, which thereby informs which program is now being executed, making it possible to manage the programs there.
Persons qualified to create programs to be installed in such one-chip microcomputers are restricted to those who are familiar with the operating system (OS) of the one-chip microcomputers and manage, own, and sell the one-chip microcomputers, or to those who have been asked to develop and create the programs and know the OS for all the programs.
Here, the OS for a one-chip microcomputer is not the OS for the CPU itself in the one-chip microcomputer, but a chip OS that takes the form of an algorithm of a program corresponding to an application and is used in a system and that defines command usage and data management method in a manner that determines how to access which data at which address in the memories around the CPU.
The instruction organization or OS for the CPU itself has been made public.
With the techniques for controlling the execution of multiple programs on the conventional one-chip microcomputer, the CPU can recognize the program being executed in the case of normal programs that tell their own IDs to the CPU according to the specific rules. When a program does not follow the specific rules, however, this causes the problem that the CPU cannot recognize the program being executed.
Furthermore, with the techniques for controlling the execution of multiple programs on the conventional one-chip microcomputer, it is impossible to inhibit one program being executed from accessing another program, and moreover, there is no need to do that. Consequently, when another invalid program has been written in the memory addresses, there is a possibility that the preceding program is rewritten, read out, or executed, which cannot be avoided technically.
Still furthermore, with the techniques for controlling the execution of multiple programs on the conventional one-chip microcomputer, when persons other than the aforementioned persons are asked to write programs, the chip OS of the one-chip microcomputer must be made known to the programmers. Accordingly, there is a strong possibility that the contents of the system will leak out, which is unfavorable in terms of security and makes it technically impossible to prevent unauthorized use of the contents from being made easily.